From 2f3835771dff512750205aa5f5f61aec0f2b8cb7 Mon Sep 17 00:00:00 2001 From: Carlos Bilbao Date: Tue, 14 Apr 2026 21:07:28 -0700 Subject: [PATCH] scsi: target: iscsi: reject invalid size Extended CDB AHS If ecdb_ahdr->ahslength is zero, two bugs follow: kmalloc(be16_to_cpu(ecdb_ahdr->ahslength) + 15, ...) allocates 15 bytes, but the immediately following memcpy writes ISCSI_CDB_SIZE (16) bytes into it, a one-byte heap overflow. Also: memcpy(cdb + ISCSI_CDB_SIZE, ecdb_ahdr->ecdb, be16_to_cpu(ecdb_ahdr->ahslength) - 1); (u16)0 - 1 promotes to (int)-1 which converts to SIZE_MAX as size_t, causing a massive out-of-bounds write. Reject ahslength == 0 with ISCSI_REASON_PROTOCOL_ERROR before the kmalloc. Also reject ahslength values that exceed the actual AHS buffer advertised. Fixes: 8f1f7d297bce ("scsi: target: iscsi: Add support for extended CDB AHS") Signed-off-by: Carlos Bilbao Reviewed-by: Dmitry Bogdanov Link: https://patch.msgid.link/20260415040728.187680-1-carlos.bilbao@kernel.org Signed-off-by: Martin K. Petersen --- drivers/target/iscsi/iscsi_target.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/drivers/target/iscsi/iscsi_target.c b/drivers/target/iscsi/iscsi_target.c index e80449f6ce15..cb832fd523af 100644 --- a/drivers/target/iscsi/iscsi_target.c +++ b/drivers/target/iscsi/iscsi_target.c @@ -995,6 +995,7 @@ int iscsit_setup_scsi_cmd(struct iscsit_conn *conn, struct iscsit_cmd *cmd, int data_direction, payload_length; struct iscsi_ecdb_ahdr *ecdb_ahdr; struct iscsi_scsi_req *hdr; + u16 ahslength, cdb_length; int iscsi_task_attr; unsigned char *cdb; int sam_task_attr; @@ -1108,14 +1109,27 @@ int iscsit_setup_scsi_cmd(struct iscsit_conn *conn, struct iscsit_cmd *cmd, ISCSI_REASON_CMD_NOT_SUPPORTED, buf); } - cdb = kmalloc(be16_to_cpu(ecdb_ahdr->ahslength) + 15, - GFP_KERNEL); + ahslength = be16_to_cpu(ecdb_ahdr->ahslength); + if (!ahslength) { + pr_err("Extended CDB AHS with zero length, protocol error.\n"); + return iscsit_add_reject_cmd(cmd, + ISCSI_REASON_PROTOCOL_ERROR, buf); + } + if (ahslength > (hdr->hlength * 4) - 3) { + pr_err("Extended CDB AHS length %u exceeds available PDU buffer.\n", + ahslength); + return iscsit_add_reject_cmd(cmd, + ISCSI_REASON_PROTOCOL_ERROR, buf); + } + + cdb_length = ahslength - 1 + ISCSI_CDB_SIZE; + + cdb = kmalloc(cdb_length, GFP_KERNEL); if (cdb == NULL) return iscsit_add_reject_cmd(cmd, ISCSI_REASON_BOOKMARK_NO_RESOURCES, buf); memcpy(cdb, hdr->cdb, ISCSI_CDB_SIZE); - memcpy(cdb + ISCSI_CDB_SIZE, ecdb_ahdr->ecdb, - be16_to_cpu(ecdb_ahdr->ahslength) - 1); + memcpy(cdb + ISCSI_CDB_SIZE, ecdb_ahdr->ecdb, cdb_length - ISCSI_CDB_SIZE); } data_direction = (hdr->flags & ISCSI_FLAG_CMD_WRITE) ? DMA_TO_DEVICE :